3500 lower is not the same as the 3400

[v6h.o.]

Last time I measured my 3500's Valves they were the same size as the 3400's.

The new LZ version 3500 does have larger valves yes. the regular 3500 does not. I'll pull them out and remeasure this week maybe to confirm again.

[SappySE107]

can you put a 3400 gasket on it?

[Guest]

The 3500 Lz heads you say wont' bolt up to a gen 3 block? It would be nice if we could get the Lz valves into the gen 3 heads.

ANy difference in combustion chamber size in the LZ heads? I need to find me a pair of these for cheap so I can gander at everythign.

[v6h.o.]

Last time I measured the 3500 valves from that engine I picked up they were still in the head so it was not as simple to measure. But they measured out what looked to me like the stock 1.76 inch intake and 1.425 inch exhaust.

I pulled one of each out of the head tonight to double check the valve sizes for the basic 3500 pushrod engine. Same sizes as a 3400 head. the measurements I just quoted above.

I'm at work right now, Came in to use the spring tool to pull them out. I'll take the head home with me again (its nice living only 5 minutes away from the d'ship) and take one of my spare 3400 head gaskets to it and take some pics.

The imprint left on the head from the ring of the 3500 head gasket measures out to roughly 3.875 inch or so in diameter.

Shaun, Just throw some 3800 series 2 valves in the head, 1.835 inch and 1.525 inch IIRC they fit the same valve guide, are the same stem size and are the same length within a few thou or so Last I remember, and use the same keeper grove location.

I have a spare set of 3800 valves that I was going to use with my last planned build up. Just have never got around to it. Engine and car are still sitting in the same local. Again been having to spend $ on the other cars to keep them running and daily drivable and House expenses and upgrades. instead of sunbird fund.. Sigh.. Never ends.

[v6h.o.]

As what is already known the bolt pattern of the 3500 head bolts is the same as the rest of the blocks. The 3400 gasket fits up just like it would on a 3400 in terms of the chamber and the head bolt holes. There is the same amount of distance between the chambers shape/edge of the chamber to the head gasket. I'll get a picture of it tomorrow if you want.

[Manitcor]

this is good news to hear, so all the bolt holes line up, is there any over lap of the combustion chamber? Also do all the coolant passages line up?

Would be sweet if you could go ahead and bolt the head to a 3400 block just to make sure though matching to the gasket should yeild enough info.

Thanks for doing all this for us.

[Hemet8]

Hybrids. Yeah!!

[El_Diablo]

pix needed!!! you might just have me swaping to a 34(.5)00



once i get a job i do plan on getting a new block to do a buildup on but i haven't been able to decide weather to stick with a 3100 or swap to the 3400, this might be making my mind up

anyone know how well the 3500 heads flow compared to the 3400?

[Guest]

Damn Colin. Thanks for the valve info. I didnt' know the 3800's were possible.

quick question on that though. Are the Valve faces flat or concave? I am hoping concave to potentially bring down the CR a bit. Which is why I like the 3500 valves. I remember from a pic you posted they have a pretty deep concave in them. A Cc or two it looks like.

[v6h.o.]

The 3800's are flat. The only thing that bugs me about the 3800 valves would be how much overlap/duration and lift that would be going on with the cam profile. as, when you push the valves out at the same time they do touch pretty damn quick (canted valves) I still have to measure out at what lifts they're hitting each other. Still might be no issue. But its something to look at before you pull a big "DOH!" when you turn it over and find out its no good after the $ spent on a custom cam and valve work.

[SappySE107]

Sivalves shows a .2 " difference in length. Are you sure its only slightly different on the heights? I dont have any 3800 parts here to look at (imagine that).

[v6h.o.]

I've got a set of 3800 valves. I do 3800 engine shit for guys around here.

Yeah its marginally different lengths. I've measured the stems and whatnot. New seats would obvoulsy have to be installed/cut. I've placed both valves together side by side and the keepers are in the same spot.

[SappySE107]

Im more interested in the 3800 valves to be cut down to our size. SI Valves still suck for quality but if the 3800 valves can be reworked, I can have it done at the machine shop here. Im definetly not sold on larger exhaust valves, and the intake may or may not be needed vs shrouding and such. That is something I will try to test out though. I believe you on the lengths and all, but the only info I could find was on their site so I figured id double check on just how much longer the 3800 valves are.

[Guest]

the valve could be longer overall but if the keeper is in the same spot from the valve face, then the portion above the keeper grooves can be machined down correct?

Machine them down to the stock height. Might have a problem if they are hollow though.

You can always port the chamber to unshroud the valves. I have done it. Tedious but possible.

[v6h.o.]

I always unshroud even the stockers. However I'll be running alot larger bore than a standard 3.4L even. So there is room to unshroud.

From what I've read for performance applications, valve sizes should be 50-52 % the size of the displacement.
However what is it for the exhaust size relative to the Intake?
Anyone know the optimum ratio of I to E valve sizes?